Organic anti-reflective coating composition and method for forming photoresist patterns using the same

ABSTRACT

The present disclosure relates to an organic anti-reflective coating composition and a method for forming photoresist patterns using the same. The anti-reflective coating compositions are useful for preventing reflection of a lower film layer or a substrate of a photoresist film, reducing standing waves caused by light and variations in the thickness of the photoresist itself, and increasing the uniformity of the photoresist patterns. More particularly, the present invention relates to an organic anti-reflective coating composition comprising particular organo-silicon based polymers and a method for forming photoresist patterns using the same. The organic anti-reflective coating composition can prevent excessive absorbency of an anti-reflective film formed therefrom and, thus, minimize the reflectivity of the film so that it can efficiently remove standing waves and increase the uniformity of the photoresist pattern.

BACKGROUND OF THE DISCLOSURE

[0001] 1. Field of the Disclosure

[0002] The present disclosure relates to organic anti-reflective coatingcompositions and methods for forming photoresist patterns using thesame. More particularly, the present disclosure relates to organicanti-reflective coating compositions comprising organo-silicon basedpolymers and methods for forming photoresist patterns using the same.

[0003] 2. Description of the Related Art

[0004] Standing waves are often generated during microfine photoresistpattern-forming processes and conventional semiconductor productionmethods. Standing waves are generated because of the optical propertiesof a lower film layer (such as, for example, the substrate of aphotoresist film) and/or because the thickness of the photoresist filmis not uniform (i.e., it is varied). Standing waves derived from lightdiffracted and/or reflected from the substrate cause reflective notchingand/or varying of the critical dimension (hereinafter referred to as“CD”) of the photoresist pattern. Accordingly, layers which preventlight from reflecting off of the substrate have been introduced betweenthe substrate and the photoresist. Such layers are calledanti-reflective films, and typically comprise materials having a highquality light-absorbing ability within a wavelength range of an exposurelight source. Anti-reflective films may generally be classified intoinorganic and organic based anti-reflective films. Organicanti-reflective films have been widely used in microfine photoresistpattern-forming processes. Organic anti-reflective films typicallypossess the following properties:

[0005] (1) After the anti-reflective film is formed and while aphotoresist comprising a photosensitive material is coated or otherwiseapplied onto the anti-reflective film, the anti-reflective film shouldnot dissolve (i.e., it is not soluble) in the photoresist solvent. Forthis reason, organic anti-reflective films generally have cross-linkedstructures (which are generated by conducting a baking process). Suchcross-linked structures also inhibit the generation of undesirablechemical by-products;

[0006] (2) In order to prevent the scattered reflection of light fromthe substrate, the film contains certain materials to absorb lightwithin a wavelength range of an exposure light source; and,

[0007] (3) The anti-reflective coating composition includes a particularcatalyst to activate the cross-linking reaction.

[0008] Thus, conventional organic anti-reflective coating compositionsgenerally comprise a cross-linking agent for generating the desiredcross-linked anti-reflective film structure, a light-absorbing agent forabsorbing light within a wavelength range of an exposure light source,and a thermal acid generator as a catalyst for activating thecross-linking reaction.

[0009] Although anti-reflective films preferably have a high absorbancefor absorbing light and inhibiting the reflection of light from thesubstrate as described above, the absorbance is not always directlyproportionate to the reflectance. On the contrary, excessively highlight absorbance may cause the amount of light which penetrates throughthe anti-reflective film to decrease and lead to an increase in thereflectance of the anti-reflective film such that it may be difficult toefficiently reduce the standing waves and obtain a quality photoresistpattern. Thus, the absorbance of organic anti-reflective filmspreferably ranges between about 0.3 and about 0.6.

[0010] Most organic materials generally contained in conventionalorganic anti-reflective coating compositions have an absorbance of morethan 0.7 with respect to a 157 nm F₂ light source. Accordingly, organicanti-reflective films formed from such compositions show excessivelyhigh absorbance with respect to the 157 nm light source and, in the caseof a microfine pattern-forming process using a 157 nm F₂ light source,the standing waves cannot be reduced such that quality photoresistpatterns can be obtained.

[0011] Due to the problems of existing organic anti-reflectivecompositions noted above, improved organic anti-reflective coatingcompositions are needed to efficiently remove standing waves and forproviding stable photoresist patterns.

SUMMARY OF THE DISCLOSURE

[0012] The present disclosure provides organic anti-reflective coatingcompositions comprising organo-silicon based polymers. The coatingcompositions prevent the absorption of the anti-reflective film frombeing too high so that it can efficiently remove the standing waves andform quality photoresist patterns.

[0013] The present disclosure also provides methods for forming aphotoresist pattern using the organic anti-reflective coatingcompositions disclosed herein. The disclosed methods may be used inmicrofine photoresist pattern-forming processes with light source,particularly a 157 nm F₂ light source, to obtain perpendicularphotoresist patterns.

[0014] According to one aspect of the disclosure, an organicanti-reflective coating composition comprises a cross-linking agent, alight-absorbing agent having a high absorbency within a wavelength rangeof an exposure light source, a thermal acid generator, an organicsolvent, and a polydimethylsiloxane polymer.

[0015] According to another aspect of the disclosure, a method forforming a photoresist pattern comprises the steps of applying an organicanti-reflective coating composition comprising a cross-linking agent, alight-absorbing agent having a high absorbency within a wavelength rangeof an exposure light source, a thermal acid generator, an organicsolvent, and a polydimethylsiloxane polymer, onto the surface of a layerto be etched to form a coating, conducting a baking process on thecoating to generate cross-linking therein and form an organicanti-reflective film, applying a photosensitive material onto theanti-reflective film to form a photoresist, exposing the photoresist toa light source to form an exposed photoresist, and developing theexposed photoresist to form the photoresist pattern.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0016] According to one aspect of the disclosure, an organicanti-reflective coating composition comprises a cross-linking agent, alight-absorbing agent having a high absorbency within a wavelength rangeof an exposure light source, a thermal acid generator, an organicsolvent, and an organo-silicon polymer.

[0017] The organo-silicon polymer may comprise a polydimethylsiloxane.Suitable polydimethylsiloxanes have a low absorbance at 157 nm (about0.1 or less). The polydimethylsiloxanes can have a weight averagemolecular weight ranging between about 14,000 grams per mol (g/mol) andabout 21000 g/mol (e.g., see The Merck Index, 12^(th) edition, pp.544 to545) and a structure in accordance with formula 1.

[0018] The organo-silicon polymer (e.g., polydimethylsiloxane) contentof the anti-reflective compositions minimizes the reflectance of a filmformed therefrom. The anti-reflective coating compositions have apreferred light-absorbency at 157 nm ranging between about 0.3 and about0.6, which allows the compositions to effectively remove standing wavesand form favorable photoresist patterns.

[0019] Ranges can be expressed herein as from “about” or “approximately”one particular value and/or to “about” or “approximately” anotherparticular value. When such a range is expressed, another embodimentincludes from the one particular value and/or to the other particularvalue. Similarly, when values are expressed as approximations, by use ofthe antecedent “about,” the particular value forms another embodiment.

[0020] The organic anti-reflective coating compositions may contain alight-absorbing agent. Preferably, the light-absorbing agent comprises apolyvinyl phenol polymer having a structure in accordance with formula2. Such polyvinyl phenol polymers have a high light-absorbance at 157 nmand contain hydroxyl groups for reacting with a cross-linking agent togenerate a cross-linked structure (i.e., the film comprises cross-linkedcovalent bonds), which will not dissolve in the photoresist solvent.

[0021] The compositions also contain a cross-linking agent or the like.Such cross-linking agents typically have a light-absorbency at 157 nmgreater than 0.7. The cross-linking agent may comprise acetal basedcompounds, more preferably, acetal polymers having a structure inaccordance with formula 3. Such acetal polymers typically have a weightaverage molecular weight ranging from about 3000 g/mol to about 100,000g/mol, and are suitable for cross-linking with a light-absorbing agent,such as polyvinyl phenol, typically contained in the anti-reflectivecoating compositions.

[0022] In formula 3, R₁ and R₂ are each independently branched and orstraight chain C₁-C₁₀ alkyl group, substituted or unsubstituted, and R₃is a hydrogen or methyl group.

[0023] Such acetal based compounds react with a light-absorbing agent(e.g., polyvinyl phenol) to form cross-linked covalent bonds in theformed organic anti-reflective films. Consequently, the disclosedanti-reflective films do not dissolve in the photoresist solvent.

[0024] The acetal polymers can be obtained by polymerizing(meth)acroleins to prepare poly(meth)acroleins, and reacting theresulting materials with a branched chain and/or straight chain,substituted or unsubstituted, C₁-C₁₀ alkyl alcohol. Such polymers andmethods for the preparation of the same have been disclosed in KoreanPatent Applications No. 99-61343 (laid-open on Jul. 5, 2001) and No.99-61344 (laid-open on Jul. 5, 2001).

[0025] The anti-reflective coating compositions generally include athermal acid generator. The thermal acid generator is a catalyst foractivating the cross-linking reaction between the cross-linking agentand the light-absorbing agent. According to one aspect of thedisclosure, the thermal acid generator comprises 2-hydroxycyclohexylp-toluenesulfonate, which has a structure in accordance with formula 4:

[0026] An organic anti-reflective film which does not dissolve in thephotoresist solvent can be formed by first coating or otherwise applyingan anti-reflective coating composition including a thermal acidgenerator on the wafer of semiconductor device and/or element. A heatingprocess such as baking is then conducted to produce acid from thethermal acid generator and, in turn, induce the cross-linking reactiondescribed above.

[0027] In the organic anti-reflective coating compositions of thepresent disclosure, the light-absorbing agent (e.g., the polyvinylphenol polymer of formula 1) may be preferably contained in an amount ofabout 50 weight percent (wt. %) to about 400 wt. %, based on the totalamount of cross-linking agent included in the present composition. Thethermal acid generator is preferably contained in an amount of about 10wt. % to about 200 wt. % relative to the amount of cross-linking agent.In addition, the organic solvent is preferably contained in an amount ofabout 1000 wt. % to about 10,000 wt. %, based on the total amount ofcross-linking agent and light-absorbing agent included in the presentcomposition. The organo-silicon polymer, e.g., polydimethylsiloxane, ispreferably in an amount of about 20 wt. % to about 100 wt. % relative tothe total amount of cross-linking agent and light-absorbing agentincluded in the composition.

[0028] Coating compositions containing an organo-silicon polymer such aspolydimethylsiloxane in the amount described above provide ananti-reflective film formed therefrom with an optimal light-absorbencyrange at 157 nm, i.e., an absorbency suitable for efficiently removingstanding waves caused by substrate reflection.

[0029] By comprising the respective components described above, theorganic anti-reflective coating composition of the present disclosurecan efficiently protect the lower film layer (i.e., the substrate of thephotoresist film) from scattered reflection. At the same time, thedisclosed anti-reflective coating compositions prevent undercutting ofthe substrate, and thereby result in high quality perpendicularphotoresist patterns.

[0030] In another embodiment of the present disclosure, the organicanti-reflective coating composition may additionally comprise anacid-diffusion inhibitor. According to one aspect of the disclosure, theacid-diffusion inhibitor may comprise a crown ether based compound suchas, 18-crown-6(1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane), which has astructure in accordance with formula 5;

[0031] Crown ether based compounds have a crown-like circular structure(as represented in formula 5) and contain oxygen atoms within such acircular structure. The oxygen atoms contained in such a compound mayoptionally interact with certain cations in the organic solvent matchingthe size of cavity in the center portion of the circular structure. Whensuch a crown ether compound is added to the coating compositions of thepresent disclosure, the compositions can prevent acid-diffusion towardthe lower portion of the photoresist, and undercutting caused by thesame, even when acid is generated during the formation of thephotoresist pattern. Thus, a quality perpendicular photoresist patterncan be obtained.

[0032] The acid-diffusion inhibitors are preferably contained in anamount of about 30 mol% to about 500 mol% relative to the amount of thethermal acid generator included in the composition (i.e., the molarratio of acid-diffusion inhibitor to thermal acid generator is betweenabout 0.30 and about 5.0).

[0033] In another aspect of the present disclosure, a method for formingphotoresist patterns comprises the steps of applying an organicanti-reflective coating composition in accordance with the presentdisclosure onto the surface of a layer to be etched to form a coating,conducting a baking process on the coating to generate cross-linkingtherein to form an organic anti-reflective film, applying aphotosensitive material onto the anti-reflective film to form aphotoresist, exposing the photoresist to a light source to form anexposed photoresist, and developing the exposed photoresist to formdesirable photoresist patterns.

[0034] Since the above photoresist pattern-forming method of the presentdisclosure uses a coating composition containing an organo-siliconpolymer such as polydimethylsiloxane, an anti-reflective film formedtherefrom may have a light-absorbency ranging from about 0.3 to about0.6 at 157 nm (using a F₂ light source), which minimizes thereflectivity of the film, and thereby effectively reduces standingwaves. Accordingly, it will be appreciated that the method of thepresent disclosure is useful for providing a superior anti-reflectivefilm suitable for use in a microfine photoresist pattern-forming processusing a F₂ light source at 157 nm.

[0035] An embodiment of method for forming a photoresist patternaccording to the present disclosure preferably includes a baking processwhich is conducted between about 150° C. and about 300° C. for about 1minute to about 5 minutes. Under such conditions, acid is generated fromthe thermal acid generator, causing the formation of cross-linkage bondswithin the anti-reflective film and, thereby producing the desiredanti-reflective film that does not dissolve in the photoresist solvent.

[0036] Moreover, in accordance with the methods of the presentdisclosure, an additional baking process(es) can be performed beforeand/or after the exposure step, preferably, in a range from about 70° C.to about 200° C.

[0037] Generally, a F₂ light source is employed in the microfinepattern-forming processes of the disclosure. However, the organicanti-reflective coating compositions and photoresist pattern-formingmethods using the same can be applied in particular microfinepattern-forming processes using a wide variety of light sources such asArF, KrF, deep-ultraviolet (DUV) including extreme ultraviolet (EUV),electron beam (E-beam), X-ray or ion beams.

[0038] Still another aspect of the present disclosure provides asemiconductor device produced using the photoresist pattern-formingmethod according to the present disclosure.

[0039] The present disclosure will be described in more detail withreference to the following comparative examples and examples, which aremerely presented for purposes of illustration and should not beconstrued to limit the scope of the appended claims.

[0040] Absorbance Values of Organic Anti-Reflective Films Prepared byConventional Methods

COMPARATIVE EXAMPLE 1

[0041] 0.13 g of a cross-linking agent having formula 6, 0.26 g of apolyvinyl phenol having formula 2, and 0.085 g of a thermal acidgenerator having formula 4 were added to and dissolved in 13 g ofpropylene glycol methyl ether acetate (solvent). The resulting mixturewas filtered through a 0.2 μm fine filter to prepare an organicanti-reflective coating composition. The obtained composition wasspin-coated onto a silicon wafer, baked at 240° C. for 90 seconds togenerate cross-linkage bonds and form an anti-reflective film. Thelight-absorbency of the obtained anti-reflective film was determined atboth 193 nm (using an ArF light source) and 157 nm (using a F2 lightsource). The absorbance values for the film of this example are providedin Table 1.

COMPARATIVE EXAMPLE 2

[0042] The procedure of comparative example 1 was repeated except theamount of polyvinyl phenol was 0.13 g instead of 0.26 g. Thelight-absorbencies were determined at both 157 nm and 193 nm using F2and ArF light sources, respectively. The absorbances for the film ofthis example are also provided in Table 1.

COMPARATIVE EXAMPLE 3

[0043] The procedure of comparative example 1 was repeated except theamount of cross-linking agent was 0.26 g instead of 0.13 g and theamount of polyvinyl phenol was 0.13 g instead of 0.26 g. Thelight-absorbency values were determined at both 157 nm and 193 nm, usingF2 and ArF light sources, respectively. The absorbances for the film ofthis example are also provided in Table 1. TABLE 1 Light-absorbancies at157 nm and 193 nm of anti- reflective films prepared by conventionalmethods. Light Comparative Comparative Comparative absorbance example 1example 2 example 3 157 nm light 0.89 0.85 0.79 source 193 nm light 0.820.70 0.48 source

[0044] Absorbance Values of Organic Anti-Reflective Films Prepared byMethods in Accordance with the Disclosure

EXAMPLE 1

[0045] 0.13 g of a cross-linking agent having formula 6, 0.26 g of apolyvinyl phenol having formula 2, 0.085 g of a thermal acid generatorhaving formula 3, and 0.13 g of a polydimethylsiloxane polymer havingformula 1 were added to and dissolved in 13 g of propylene glycol methylether acetate (solvent). The resulting mixture was then filtered througha 0.2 μm fine filter to prepare an organic anti-reflective coatingcomposition. The obtained composition was spin-coated onto a siliconwafer, baked at 240° C. for 90 seconds to generate cross-linkage bondsand form an anti-reflective film. The absorbance of the obtained filmwas determined at 157 nm as above. The absorbance value at 157 nm forthe film of this example is provided in Table 2.

EXAMPLE 2

[0046] The procedure of example 1 was repeated except the amount ofpolyvinyl phenol was 0.13 g instead of 0.26 g. The absorbance at 157 nmwas determined for the obtained film and is provided in Table 2.

EXAMPLE 3

[0047] The procedure of example 1 was repeated except the amount ofcross-linking agent was 0.26 g instead of 0.13 g and the amount ofpolyvinyl phenol was 0.13 g instead of 0.26 g. The light-absorbance forthe resultant film was determined at 157 nm and is given in Table 2.TABLE 2 Light-absorbencies at 157 nm of anti-reflective films preparedby the methods in accordance with the present disclosure Lightabsorbance Example 1 Example 2 Example 3 157 nm light source 0.54 0.480.58

[0048] As can be seen from Table 1, organic anti-reflective filmsprepared by conventional methods require that the relative compositionsof cross-linking agent and light-absorbing agent be carefully controlledin order to have a desirable light absorbance between about 0.3 andabout 0.6 with respect to a 193 nm ArF light source. The absorbancevalue of the film of comparative example 3 can be attributed to therelatively low light-absorbency of the cross-linking agent at 193 nmArF. However, the cross-linking agent and the light-absorbing agent haveabsorbance values of 0.7 or more with respect to a 157 nm F2 lightsource, and the absorbances of the anti-reflective films are too highfor use in a microfine pattern-forming process with a 157 nm F lightsource.

[0049] On the other hand, the anti-reflective coating compositionsaccording to the present disclosure comprise a polydimethylsiloxanepolymer having an absorbance of 0.1 or less of with respect to a 157 nmlight source. The anti-reflective coating compositions of the disclosureprovide anti-reflective films having a light-absorbency at 157 nm in thepreferred range between about 0.3 and about 0.6, and having a minimumreflectivity value. Thus, the coating compositions of the presentdisclosure provide an anti-reflective film that is efficient ineliminating reflection from the substrate of the photoresist film andremoving standing waves, and the films produced therefrom are useful forforming quality photoresist patterns.

[0050] Additionally, the present disclosure provides organicanti-reflective films which are useful in microfine pattern-formingprocesses that use a 157 nm F2 light source. Microfine pattern-formingprocesses that use a 157 nm F2 light source are expected to be theprinciple process for forming photoresist patterns in the future.

[0051] It is further understood by those skilled in the art that theforegoing description provides preferred embodiments of the organicanti-reflective compositions and methods for forming a photoresistpattern disclosed herein. Various changes and modifications may be madeto the disclosure without departing from the spirit and scope thereof.

What is claimed is:
 1. An organic anti-reflective coating compositioncomprising: a cross-linking agent; a light-absorbing agent having a highlight-absorbency within a wavelength range of an exposure light source;a thermal acid generator; an organic solvent; and a polydimethylsiloxanepolymer having a structure in accordance with formula
 1.


2. The composition according to claim 1, wherein the light-absorbingagent comprises a polyvinyl phenol polymer having a structure inaccordance with formula
 2.


3. The composition according to claim 1, wherein the cross-linking agentcomprises a polymer having a weight average molecular weight rangingfrom about 3000 grams per mol (g/mol) to about 100,000 g/mol and astructure in accordance with formula
 3.

wherein R₁ and R₂ are each independently a C₁-C₁₀ alkyl group, straightchain or branched; and R₃ is a hydrogen or methyl group.
 4. Thecomposition according to claim 1, wherein the thermal acid generatorcomprises 2-hydroxycyclohexyl p-toluenesulfonate having a structure inaccordance with formula
 4.


5. The composition according to claim 2, wherein the polyvinyl phenolpolymer is contained in an amount of about 50 weight percent (wt. %) toabout 400 wt. %, based on the amount of the cross-linking agent.
 6. Thecomposition according to claim 4, wherein the thermal acid generator iscontained in an amount of about 10 wt. % to about 200 wt. %, based onthe amount of the cross-linking agent.
 7. The composition according toclaim 1, wherein the organic solvent is contained in an amount of about1000 wt. % to about 10,000 wt. %, based on the total amount of thecross-linking agent and the light-absorbing agent.
 8. The compositionaccording to claim 1, wherein the polydimethylsiloxane polymer iscontained in an amount of about 20 wt. % to about 100 wt. %, based onthe total amount of the cross-linking agent and the light-absorbingagent.
 9. The composition according to claim 1, further comprising anacid-diffusion inhibitor.
 10. The composition according to claim 9,wherein the acid diffusion inhibitor comprises (18-crown-6(1, 4, 7, 10,13, 16-hexaoxacyclooctadecane) having a structure in accordance withformula 5;


11. The composition according to claim 9, wherein the molar ratio ofacid-diffusion inhibitor to thermal acid generator is between about 0.30and about 5.0.
 12. A method for forming a photoresist pattern comprisingthe steps of: applying an organic anti-reflective coating compositioncomprising a cross-linking agent, a light-absorbing agent having a highabsorbency within a wavelength range of an exposure light source, athermal acid generator, an organic solvent, and a polydimethylsiloxanepolymer onto the surface of a layer to be etched, to form a coating;conducting a baking process on the coating to generate cross-linkingtherein and form an organic anti-reflective film; applying aphotosensitive material onto the anti-reflective film to form aphotoresist; exposing the photoresist to a light source to form anexposed photoresist, and, developing the exposed photoresist to form thephotoresist pattern.
 13. The method according to claim 12, wherein thebaking process is performed between about 150° C. and about 300° C. forbetween about 1 minute and about 5 minutes.
 14. The method according toclaim 12, further comprising an additional baking process before orafter the step of exposing the photoresist to a light source.
 15. Themethod according to claim 14, wherein the baking process is performedbetween about 70° C. and about 200° C.
 16. The method according to claim12, wherein a microfine photoresist pattern is formed and the lightsource is selected from the group consisting of F₂, ArF, KrF,deep-ultraviolet including extreme ultraviolet, electron beam, X-ray,and ion beam.
 17. A semiconductor device manufactured by the method ofclaim 12.